Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 151

The pharynx is a muscular tube running from the nasal cavity to the larynx (voice box) and is often simply referred to as the throat. It consists of three sequential sections: nasopharynx, oropharynx and laryngopharynx.

The nasopharynx is the superior portion of the pharynx, which begins at the nasal cavity. It continues the process of conditioning the inspired air and, like the nasal cavity, contains a ciliated epithelium which continues the trapping and removal of particulates. The tonsils form a ring of lymphoid tissue around the pharynx; these contain populations of immune cells called macrophages which monitor the airway and trap potential pathogens such as bacteria.

There are four groups of tonsils: the pharyngeal tonsils, or adenoids, are situated superiorly and posteriorly in the nasopharynx; the tubal tonsils sit close to the openings of the Eustachian tubes which connect to the middle ear (Chapter 6); the lingual tonsils are embedded in the root of the tongue; and the palatine tonsils are located on either side of the oropharynx. It is the almond-shaped palatine tonsils that frequently become infected and often purulent during tonsillitis.

Figure 4.2 The components of the upper respiratory tract

The middle portion of the pharynx, which lies posterior to the oral cavity, is called the oropharynx. This section is part of both the respiratory and digestive systems and is lined by a thicker, non-ciliated, stratified squamous epithelium to resist the abrasive effects of swallowing food and liquids.

The final section of pharynx is called the laryngopharynx because it is continuous with the larynx. As with the oropharynx, it is part of both the respiratory and digestive tracts and is lined by the same type of robust stratified squamous epithelium.

Since these final two sections of the pharynx form a common passageway for air, food and water, there is a danger of the airway becoming occluded should food become stuck when swallowing (deglutition). Difficulty with swallowing is termed dysphagia and this becomes more common with age, increasing the risk of choking and the aspiration of food into the airway.

Obesity is an increasing problem in the UK and is associated with upper airway dysfunction. To further your understanding of this issue, read through the following case study.